unidentified v6

[Mowdigger]

Today I made a trip to a local salvage yard and made a couple good scores. I got a firewall heater box and a heater control and a few other small things all for 30.00 . While I was there I ran across a 70 C20 that had a large V6 in it. It is complete with a tranny behind it. Does anyone know anything about these? I'll try to post a pic of one I found here in a previous post.

[Stocker]

Looks like a GMC V6 http://www.6066gmcguy.org/gmcv6a.htm

I believe pickups got 305 cubic inch engines, with bigger displacement engines available in larger trucks.

[classic5liter]

I own one of those, its alot cleaner though [painted orange]. Enough torque to tear a farmhouse off its foundation if you could choke it up right and had the right traction.

According to the serial numbers the one in my 68 C2500 GMC is a 351-E with the 'magnum' heads and Stromberg WWC 2-bbl carb w/manual choke.

That truck does not have the same carburetor as mine. That is perhaps a 305 or a different version of the 351.

You should see the monstrous flywheel and the two very heavy adaptor rings to make this engine work with that turbo 400 [see the downshift switch], quite interesting.

I wish I could appreciate that big block GMC V-Six but I put about 6,500 miles on mine and I don't really like it, plus after timing and tuning mine completely, I notice it knocks under load. At first thought I beleived this was a gas ping, but after several timing adjustments even to extremes and then returning it to the correct, it still does, but only under load [hills, pulling into traffic] I miss my 454 silverado, I guess is what it is.

That engine right there made my 68 very inexpensive. And was otherwise reliable.

There is alot of support out there for those engines if you own one and like it, and there are some very knowledgeable V-Six owners and lovers on this forum.

[292farmer]

usually on the front of the drivers side head it will say motor ci 305 351 401 etc. and possibly an m for magnum, or just a c. Thats how it is on my c60 and my dads two spare motors hope that helps!

[292farmer]

also check this site has info parts and possibly more u need
http://thunderv12.com/ the v12 was two 351v6 put together!!

[factorystock]

The V6 engine was never designed to be put in cars, its purpose was deliver maximum torque at low rpms, a principle found in long life diesel truck engines. The V6 was punched out to 478 in the largest 80 series trucks, where it put out 442 lbs torque @ 1400 rpm, compared the largest Chevy V8 truck engine the 427, which put out 405 lbs @ 2400 rpm. The V6 put out maximum torque at 1000 rpms lower than a V8. These engines could handle a higher ratio rear axle. The 3.07 was standard ratio for 1/2 ton V6 GMC pickups, while the chevy had to use 3.73 for there 6 cyl. 1/2 ton. The 3/4 ton V6 GMC pickup used a 4.10 rear end while the 6 cyl Chevy pickup used a 4.57 standard. When the 351 V6 came out in 1966, the 3/4 tons should have been equipped with the 3.54 ratio, but that did not happen. It wasn't till 68, the last year of the V6 that the 3.54 ratio became optional on 3/4 ton V6's. This change allowed a jump in gas mileage from 8 mpg to 12 mpg.These engines were designed to run slow@ 2400rpm, so the wrong ratio rear axle resulted in poor mileage and unhappy owners.The market changed in the late 60's, so V8's became the engine of choice for most buyers.

[andrewmp6]

Yeah the gmc v6 is odd but a torque monster most of them made max torque at 1500rpms.The v12 gmc made they was in like firetrucks or even used for water pumps.

[Longhorn Man]

68 wasn't the last year for it the 305, my old 69 GMC had it originally. The VIN started off CM******* it was a 305/TH400/3.07 The guy I got it off of said the 305 lasted a little over 300,000 miles, never opened up, and was pulled for something more fun (400 small block/TH350).

[BobS]

Are you sure it was a 70? 69 was the last year for the V-6 to be factory-installed but it could still be dealer-installed through 72. If it's a 70, I'd be interested in seeing what the VIN is, I've always been curious as to how dealers handled that issue. But then, it may have been installed later by one of it's previous owners. Automatic too!

Bob

[factorystock]

Nice catch Longhorn Man, I should have been more specific, 1968 was the last year for the 351 V6 in pickups, 1969 was the last year for the 305 V6 in pickups. The large truck V6's ended in 1974.

[Mowdigger]

Here is the VIN# of the truck it was in. CE240J101129
The picture I posted was not the actual motor, it looks just like that though. I noticed that the power steering pump had been cobbled on at some point, that made me think that this engine had been put in by the previous owner.

[Mowdigger]

Also, is there any availability of parts to rebuild one of these?

[BigChevy80]

My uncle's neighbor has a 351 V6 in an old C65 grain truck from the late 60's. The thing will only do about 53 MPH maxed out, but would pull the world if you could put a rope around it. They only use it during harvest season for 2-3 weeks a year, so it doesn't see many miles. Last time I drove it 3 seasons ago it only had about 65,000 miles on it.

Truly one of the most heavy duty gas engines ever put in a truck...

[292farmer]

available parts from my experience is small however that website in one of my early replies has a lot of parts theve collected over time.

[BobS]

There are lots of parts available for these engines but you may have to look a little to find them. Most parts counter guys won't know what you're talking about, makes for some interesting conversations.

Bob